The present study was aimed to use spent wash as a substitute for expensive commercial media for Rhizobial cultures. Growth of Rhizobium strains at different concentrations of spent wash was observed and found maximum at 50% spent wash. Bacteria were grown on 50% spent wash which produced remarkable results and competed with standard media like tryptone yeast extract, Rhizobium minimal and yeas...

Parasponia, a woody member of the elm family, is the only nonlegume genus whose members are known to form an effective nitrogen-fixing symbiosis with a Rhizobium species. The bacterial strain RP501 is a slow-growing strain of Rhizobium isolated from Parasponia nodules. Strain RP501 also nodulates the legumes siratro (Macroptilium atropurpureum) and cowpea (Vigna unguiculata). Using a cosmid clo...

Cosmids containing hydrogen uptake genes have previously been isolated in this laboratory. Four new cosmids that contain additional hup gene(s) have now been identified by conjugal transfer of a Rhizobium japonicum 122DES gene bank into a Tn5-generated Hup(-) mutant and screening for the acquisition of Hup activity. The newly isolated cosmids, pHU50-pHU53, contain part of the previously isolate...

The evolution of mutualisms under novel selective pressures will play a key role in ecosystem responses to environmental change. Because fixed nitrogen is traded in plant–rhizobium mutualisms, increasing N availability in the soil is predicted to alter coevolution of these interactions. Legumes typically decrease the number of associations (nodules) with rhizobia in response to nitrate, but the...

A reduction in the viability of cowpea rhizobia was observed when Rhizobium trifolii IARI and cowpea Rhizobium strain 3824 were inoculated together in soil. The reduction in number of cowpea rhizobia in soil was found to be associated with the reduction in number of nodules per plant and retardation in plant growth. An antimicrobial substance was isolated from R. trifolii which, on electron mic...

Sigma 54-dependent transcriptional activators such as Escherichia coli NtrC, Rhizobium meliloti NifA, and Rhizobium leguminosarum DctD share similar central and carboxy-terminal domains but differ in the structure and function of their amino-terminal domains. We have deleted the amino-terminal and carboxy-terminal domains of R. leguminosarum DctD and have demonstrated that the central domain of...

A procedure was designed which enabled the detection of ex planta nitrogenase activity in the fast-growing cowpea Rhizobium strain IHP100. Nitrogenase activity in agar culture under air occurred at a rate similar to that found for Bradyrhizobium strain CB756 but lower than that for Rhizobium strain ORS571. Hybridization studies showed that both nod and nif genes were located on a 410-kilobase S...

∗Corresponding author. E-mail: [email protected] Abbreviations: AGP, Arabinogalactan protein; GPI-anchor, Glycosylphosphatidylinositol lipid anchor; HRGP, Hydroxyproline-rich glycoprotein; IT, Infection thread; NF, Nod-factor (Lipochitin oligosaccharide); LPS, lipolysaccharide; PRP, proline-rich protein; UDP, uridine diphosphate Colonization of host cells by rhizobium bacteria involves th...